This invention relates in general to milling machines and in particular to three-axis milling machines.
The technology associated with machine tools is extensive and diverse. Known in the art are one, two and three-axis machines, some of which grind or mill, others of which drill or bore. The types of attachments and options are almost as varied as the number of different machines. The following list of patents gives a brief indication of some of these various types of machines and features:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 3,555,963 Evans 1/19/71 3,617,142 DeWane 11/02/71 3,157,283 Maass et al. 11/17/64 2,963,057 Morse 12/06/60 2,883,890 Fink et al. 4/28/59 2,365,068 Gerbig 12/12/44 ______________________________________
Evans discloses a multiple spindle transfer machine having a removable spindle tool holder and in which a single drive motor is used to drive each spindle through a gearing arrangement. The entire tool head moves in a vertical direction by means of a worm gear and pinion drive using guides and slides on each side thereof.
DeWane also discloses a vertically movable head in which a DC drive motor is geared to drive the tool spindle. The head is mounted to the structure by a slideway arrangement and movement occurs by use of a counterbalancing weight and pulley arrangement.
Each of these patents disclose conventional slideway or guide means for controlling the alignment of the vertical travel. Such means require accurate machining, lubrication and major overhaul by replacement or remachining when they become worn. Furthermore, each of these two patents utilize gearing to transfer the rotary motion of the motor shaft to drive the tool spindle.
The remaining four patents are listed as being of only general applicability to conventional three-axis machine tools. Each of these patents disclose a particular unique application or feature which might be associated with a particular machine tool.
The following list of patents deals with drive units and mechanisms which have hollow shaft motors or the like:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 1,636,560 Hall 7/19/27 1,967,045 Wehmeyer 7/17/34 2,500,175 Guthrie 3/14/50 2,571,267 Ljunggren 10/16/51 2,703,847 Kalikow 3/08/55 2,772,546 Barrows 12/04/56 3,854,063 Bergman 12/10/74 3,987,322 Bourgain et al. 10/19/76 2,714,866 Pleuger et al. 8/09/55 ______________________________________
The Hall patent discloses a hollow shaft motor employed for a valve seat grinder in which the hollow shaft is used to accommodate a pilot stem.
The Wehmeyer patent relates to machine tools only in that it includes a chuck-operating motor which is mounted on a lathe spindle.
The Ljunnggren patent discloses a thread-spinning spindle having a hollow shaft motor drive for the blade which drives the spool through a flexible coupling.
The remaining patents are of only general applicability in that they do not relate to conventional drive motors for use with three-axis machine tools. In addition, none of these listed patents involves the concept of the coaxial coupling of a conventional solid output shaft of a motor to a hollow tool chucking spindle. This particular coaxial coupling concept provides the advantages of individually replaceable parts, without having to replace the entire assembly, and the ability to use standard, commerically available motors.
U.S. Pat. No. 2,028,727 issued Jan. 21, 1936 to Perry et al. discloses a particular construction of machine tools wherein the tools are distinctly segregated into a number of major structural units. One aspect of this segregation is that the tool head is readily detachable from a saddle member and the saddle member is readily detachable from the vertical support column of the subject machine tool. Although the saddle member is slidable on the ways of the vertical column, this design in no way solves the problems of machining accuracy, lubrication and wear associated with such slide and guide arrangements as previously discussed.
The following two listed patents are of only general interest and are not believed to be relevant to three-axis machine tools:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 2,734,359 Mulheim 2/14/56 2,242,475 Misuraca 5/20/41 ______________________________________